This invention relates to an apparatus and a process for electroplating a plurality of pre-selected isolated areas on incremental segments of an elongate metal strip while maintaining the rest of the strip out of contact with the electroplating bath. More particularly, the invention relates to a means for providing controlled advancement of the strip as each segment is positioned for exposure to the electroplating bath.
In many electroplating operations, e.g. operations wherein microcircuits are electroplated with gold, there is a need to minimize the amount of expensive metal utilized by closely restricting its deposition to only those surface areas where its presence is essential. It is desirable, however, that such selective deposition of the metal achieved without resorting to procedures which greatly restrict the production rate of an electroplating facility or to procedures which greatly increase the handling costs of the items being electroplated.
It has been known to use organic coatings to mask those areas of metallic substrates on which electroplating is not required and thereby avoid those areas being electroplated. After electroplating of such partially masked items is finished, the masking material is removed, leaving discrete electroplated zones. Such a process requires expensive coating and stripping steps. These steps add to the cost of the electroplating operation and also increase the probability that some of the costly work product will have to be scrapped because of damage incurred during the manufacturing operations.
The most suitable apparatus of the solution of such problems are disclosed in the commonly-owned and co-pending United States Patents to Kosowsky et al. Such apparatus uses seal means to selectively isolate the surface of sheet which are to be exposed to contact with the electroplating fluid. The latter of these applications describes means to continuously electroplate an elongate suitable for use on very large runs of a strip with a particular metallic pattern; however, it has been found to be inconvenient to modify the sealing parts of such apparatus to accommodate a series of smaller runs of strips of different configurations. Another drawback to this continuous plating-type of apparatus is that it requires a relatively large amount of space because the various processing steps must be carried out as the strip moves through processing stations elongated to compensate for the movement of the strip. Therefore, it is desirable, for smaller orders, to construct apparatus for the intermittent electroplating of elongate strips which will allow the strips to be advanced step-by-step. Consequently, the strips must be stationary during the electroplating procedure.
One means of achieving such step-by-step advancement is described in U.S. Pat. No. 3,788,963, and commonly-owned and co-pending U.S. application Ser. No. 400,153 filed on Sept. 23, 1973 by Kosowsky et al. In this patent and application, a novel advancement is achieved using a sensing means and a vibration-dampening vise to establish, respectively, (1) that the strip was positioned properly on each forward movement thereof and (2) vibrations from winding means were not transmitted back to the electroplating bath. This system performed very well; nevertheless, there was sufficient machine downtime caused by the occasional movement of the strip out of register that it was thought desirable to provide an apparatus that would have an improved advancement means, one that would have the advantage of avoiding misplaced plating of valuable metals, an attribute of the earlier apparatus, but also machine that would substantially eliminate the need for periodic shut-downs necessary for realigning the tape.